Thanks for the info all. And for confirming what I was pretty sure was the issue.

The thermostat sounded interesting but I think it was done not too long ago and I have not had any poor mileage issues that most report with that. I'll check temps anyway just to be 100% sure.

I agree, rheingold is looking like a must. I'll start trying to find a copy or pay them the $100 for it. I think my Carly cables will work with it... I hope anyway.

Thanks for the tips blue_dragon... I follow your posts in most of my research on the diesels (you've held on to and run yours longer than most tend to it seems) and came across your thread.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)